GAMMALN function
This article describes the formula syntax and usage of the GAMMALNfunction in Microsoft Excel.
Description
Returns the natural logarithm of the gamma function, Γ(x).
Syntax
GAMMALN(x)
The GAMMALN function syntax has the following arguments:

X Required. The value for which you want to calculate GAMMALN.
Remarks

If x is nonnumeric, GAMMALN returns the #VALUE! error value.

If x ≤ 0, GAMMALN returns the #NUM! error value.

The number e raised to the GAMMALN(i) power, where i is an integer, returns the same result as (i  1)!.

GAMMALN is calculated as follows:
where:
Example
The example may be easier to understand if you copy it to a blank worksheet.
How do I copy an example?

Select the example in this article. If you are copying the example in Excel Web App, copy and paste one cell at a time.Important Do not select the row or column headers.
Selecting an example from Help

Press CTRL+C.

Create a blank workbook or worksheet.

In the worksheet, select cell A1, and press CTRL+V. If you are working in Excel Web App, repeat copying and pasting for each cell in the example.

Important For the example to work properly, you must paste it into cell A1 of the worksheet.

To switch between viewing the results and viewing the formulas that return the results, press CTRL+` (grave accent), or on the Formulas tab, in the Formula Auditing group, click the Show Formulas button.

After you copy the example to a blank worksheet, you can adapt it to suit your needs.

